(1) Field of the Invention
The present invention relates to a thermoplastic resin composition. More specifically, the present invention relates to a thermoplastic resin composition having a high heat resistance and an excellent impact strength. The thermoplastic resin composition of the present invention can be advantageously used in the fields of automobile parts, for example, interior trims such as meter hoods, meter clusters, instrument panels and console boxes, and exterior trims such as bumpers, exterior plates and lamp housings, and for various machine parts.
(2) Description of the Related Art
It is known that a copolymer of an aromatic vinyl compound, especially styrene, with maleic anhydride has a higher glass transition temperature and a higher heat distortion temperature, compared with commercially available styrene resins, but this copolymer has inferior mechanical properties, especially impact resistance, and is very brittle. Accordingly, the copolymer can be practically used only over a very limited range.
As the means for improving the impact resistance of the aromatic vinyl compound/maleic anhydride copolymer, there is known a process in which a rubber component is introduced into the copolymer. For example, British Patent No. 1,402,323 discloses a process in which a vinyl aromatic compound is copolymerized with maleic anhydride in the presence of a rubber; Japanese Unexamined Patent Publication No. 54-50553 discloses a process in which a third component such as an aromatic polycarbonate and/or an aromatic polyallylate is blended together with the rubber component; and Japanese Unexamined Patent Publication No. 54-28355 and U.S. Pat. No. 4,269,950 disclose a process in which the impact resistance is improved by an introduction of an ABS resin (acrylonitrile/butadiene/styrene copolymer resin), a rubber-modified polystyrene resin or an MBS resin (methyl methacrylate/butadiene/styrene copolymer resin).
In the process in which a rubber component is introduced, to improve the impact resistance of the aromatic vinyl compound/maleic anhydride copolymer, control of the polymerization system becomes difficult as the result of this introduction of the rubber component, and only a limited amount of the rubber component can be used. In the process in which a third component is blended together with the rubber component, not only the above-mentioned disadvantages but also an economical disadvantage occurs. Moreover, in the improvement process comprising the introduction of an ABS resin or the like, the improvement of the impact resistance is not satisfactory, and thus a further improvement is desired.